It will be tempting for outsiders to look at the Liberal Democrats this week and see them as a broken ship adrift on the stormy ocean – and a pretty wild ocean it was at Brighton on Monday, as westerly gales ripped through the Channel. Repeatedly decimated in the local elections, derided on both the left and the right, and down in the opinion polls – this morning's 14% in ICM masks an average of 10% among all polls – it is not hard to imagine the Lib Dems coming to their autumn conference as a sullen and even mutinous crew, increasingly anxious to set a new course under a different skipper into easier waters.

In reality, the mood at Brighton is proving steadier than many outsiders expected. But it is not a naive mood. The Lib Dem party signed up for a difficult but exciting voyage into the unknown under Captain Clegg in 2010. In spite of the damage they have suffered, they remain willing to continue serving under him on his terms. It is, after all, a long voyage. Plenty of the crew certainly mutter that First Officer Cable would make a better helmsman. But though that muttering is on the increase, it is also only heard in private. The Lib Dems are a disciplined lot and they seem to sense that this question, though potentially a relevant and important one, is for later. This is a long voyage. They are not about to abandon ship.

Mr Cable knows all this. His speech on Monday was that of a man who would certainly like to do things differently in many ways. When he said the central point was that the country must not get stuck on a downward escalator in which low growth leads to bigger deficits, more cuts and lower growth, calling this "the way to economic disaster and political oblivion", it was a shot across the bows of George Osborne and perhaps even some Liberal Democrat ministers too. When he invoked "liberal and social democratic principles" and said the party should be willing "to work with other parties in the wider national interest", it was clear he was not just talking about working with the Conservatives.

Mr Cable also delivered the speech of a man who has certainly not given up on the possibility of leading his party, but who wants to choose his moment, if it comes at all, and to keep hold of a situation which could rapidly spin out of control if he says or does anything to encourage a premature explosion. That intention was evident in the conference economic debate yesterday, in which ministers and party heavyweights repeatedly came to the microphone to oppose any attempt to scrap the coalition's fiscal commitments.

Their efforts were overwhelmingly successful when the issue came to the vote, yet the difference between the desire for sustainable growth expressed by the defeated minority in the debate and the desire for sustainable growth expressed by Mr Cable and the majority is more than a little cryptic. The conclusion, pretty clearly, is that the party leadership wants to retain strict control over any such moves – not to allow the conference to set things running.

Fair enough. A lot could go wrong if the public and the markets think the Lib Dems are suddenly running away from their coalition agreement. Yet the Lib Dems still have to find a way of differentiating their economic message to the public. There was plenty of that in Mr Cable's deft and well-balanced speech.

But the Lib Dems are a political party that has to face the voters again in 2015. Unless they have a better story to tell the voters, they are going to suffer some pretty serious losses, as all the polls, including the ICM poll this morning, underline. That's why the possibility that Mr Cable might save seats that at the moment look likely to be lost under Mr Clegg is not an idle one.

This morning's poll shows that a change of leader might offer the Lib Dems an electoral dividend that could make a palpable difference. Perhaps they can afford to resist that thought now. But if things have not changed in a year's time, it will be harder to do the same thing then.